whenever possible.
I've had former employees be referral sources.
I can think of 2 former employees who I don't have a positive relationship with: (1) a receptionist who worked for 2 weeks and got up and left in the middle of the day w/ no notice when I was at a conference and then subsequently tried to claim she worked for our office for 4 months and was laid off; and (2) an employee who had an exceptionally difficult personality who had charged a dress and other apparel to her hotel room on a company trip and then when COVID hit was busted being logged into work while she was out running errands with her boyfriend.